32O RESEARCH SEMINAR. 



remodeled into a large one. Section of the nerve at the base of 

 the small chela inhibits this reversal, wholly or partially. 



With regard to the internal factors which induce this reversal 

 it seems at first sight that the nervous system must be the con- 

 trolling one. Histological examination shows the following 

 facts : (i) Nerves of the right and left sides are not morpholog- 

 ically different except that they branch differently in the two 

 types of claw. (2) During regeneration or remodeling changes 

 occur in their definitive places, i. e,, growth does not occur at one 

 end only. (3) The nervous shock of amputation may produce a 

 weakness of the cut side, and also add to the nutriment of the other 

 side of the ganglion, thus inducing reversal. (4) The nerve evi- 

 dently carries the stimulus to grow, but may be only passive. (5) 

 The cutting of the nerve in the claw may cause a general disease 

 of that organ, such as might be caused by injuring the musculature, 

 and thus prevent perfect reversal. 



It appears, therefore, that we must not attribute to the nervous 

 system as much importance in the remodeling as would seem at 

 first sight necessary when it is found that section of the nerve 

 inhibits reversal. 



August 12. The Development of the Vascular System of Ce- 



ratodus. By WM. E. KELLICOTT. 



The vascular system of the adult Ccratodns shows resem- 

 blances to both the elasmobranchs and the amphibia. It was 

 thought that the investigation of its development might throw 

 some light upon the significance of this curious combination. A 

 few of the points of interest which appeared in the course of the 

 study are the following : 



The heart develops similarly to that of the frog or Urodelc, 

 from a pair of folds of the splanchnopleure, the somatopleure 

 forming the pericardium. 



The branchial arteries also develop similarly to those of the 

 amphibia. They are four in number and early form continuous 

 passages from the ventral to the dorsal aorta. Later they divide 

 into the afferent and efferent vessels and finally each efferent di- 

 vides, forming the two efferent branchials characteristic of the 

 adult. The vessels of the hyoid arch are well developed early, 



